This invention relates to a system for converting waste heat from an internal combustion engine of a vehicle to provide additional power for the vehicle. More particularly, this invention relates to a vehicle waste heat conversion system including a vapor engine which is coupled to the drive train of the vehicle through a motor-generator where the motor-generator is connected to a battery which it can charge or from which it can draw power.
Significant effort has been directed toward developing systems that use the energy present in the waste heat produced by internal combustion engines. The patent literature discloses several examples of proposed systems for recovering internal combustion engine waste heat. For example, U.S. Pat. No. 3,948,053 by Gamell describes a system that uses exhaust heat to generate vapor for powering a supercharger. Berg, in U.S. Pat. No. 4,031,705 describes a heat conversion system having a vapor engine that mechanically communicates with the crank shaft of an internal combustion engine via an one way clutch. The vapor engine of Berg""s system is powered by a working fluid in a Rankine circuit that is heated by waste heat from the internal combustion engine coolant and then boiled by engine exhaust waste heat.
A heat conversion system described by Anderson and Nation in U.S. Pat. No. 4,351,155 uses two Rankine circuits having two distinct working fluids. One of the working fluids of the Anderson and Nation system is adapted for boiling at the relatively low temperature of the internal combustion engine liquid coolant. The other working fluid of the Anderson and Nation System boils at the higher temperature of the engine""s exhaust. Hunt, in U.S. Pat. No. 4,470,476, describes hybrid vehicles having multiple power plants. The claims of Hunt""s patent are directed at a system that generates electricity from engine exhaust waste heat using a thermoelectric device. The drive train of Hunt""s system can be alternately or simultaneously powered by a primary internal combustion engine and an electric motor.
U.S. Pat. No. 4,901,531 issued to Kubo and Ghuman teaches a combination diesel/Rankine engine having a diesel portion with five diesel cylinders and one Rankine cylinder. The Rankine cylinder of Kubo and Ghuman""s engine expands vapor that is generated in a boiler heated by the waste heat from the diesel portion of the engine. U.S. Pat. No. 5,327,987 issued to Abdelmalek teaches a vehicle having a waste heat powered vapor engine that turns an electric generator. Abdelmalek""s vapor powered electric generator can charge a battery or drive an electric motor that is connected to a portion of the drive train of the vehicle. The electric battery of Abdelmalek""s system can also power the drive motor when the vapor engine is not producing power.
The foregoing are examples of useful systems for recovering internal combustion engine waste heat. However, none of the above described systems mechanically link a vapor engine and a unit combining the functions of a motor and a generator and then mechanically connect the resulting power module with a vehicle drive train to augment drive train power between the vehicle transmission and the vehicle drive wheels.
The invention waste heat conversion system features a motor-generator that is directly coupled to a waste heat converting vapor engine and the drive train between a vehicle transmission and the vehicle drive wheels. The invention system is capable of numerous modes of operation including a mode for converting waste heat to mechanical power that can be added to the drive train, a mode for converting waste heat to electrical power for storage in a battery, a mode where battery power is used to add power to the drive train and a mode for converting braking energy for storage in a battery.
The invention system converts waste heat primarily from the internal combustion engine exhaust stream into useful work by directing hot exhaust gas through a boiler where high pressure working fluid is converted into high pressure vapor. The invention system uses the exhaust stream as a source of heat because the exhaust stream usually carries most of the waste heat of an internal combustion engine. An exhaust bypass valve diverts hot exhaust gas around the boiler when high pressure vapor is not needed. In the invention system, the vapor engine is mechanically coupled to the motor-generator by a one way clutch. The vapor engine includes a vapor engine bypass valve that controls the supply of vapor to the vapor engine. The one way clutch between the vapor engine and the motor-generator allows the vapor engine to turn the motor-generator but does not allow the motor-generator to turn the vapor engine. The motor-generator is directly coupled by an engageable clutch to a portion of the vehicle drive train between the vehicle transmission and the drive wheels. The motor-generator is connected to a battery through a voltage regulator. The voltage regulator can function in three modes: a first mode where current flows from the motor-generator to the battery to charge the battery, a second mode where current flows from the battery to the motor-generator to power the motor-generator, and a third, neutral mode where the motor-generator turns freely as no current passes between the motor-generator and the battery.
The invention system also includes a control module that receives signals from sensors and then sends signals to control the operations of the vapor engine bypass valve, the engageable clutch and the voltage regulator. The control module receives signals from a power setting sensor that responds to the internal combustion engine throttle setting, a drive shaft rotation sensor that detects drive shaft rotation which occurs when the vehicle is moving, a brake activation sensor that detects brake activation, a battery charge sensor that measures the degree of battery charge and a vapor pressure sensor that measures the pressure of vapor produced by the boiler. The control module responds to signals from these sensors and directs the operations of the vapor engine bypass valve, the exhaust gas bypass valve, the voltage regulator and the engageable clutch so that the system operates in one of at least four modes: (1) a first mode where the my engageable clutch is engaged and the vapor engine turns the motor-generator to provide power to the drive train, (2) a second mode where the clutch is disengaged and the voltage regulator is activated to transfer current from the motor-generator to charge the battery as the vapor engine turns the motor-generator, (3) a third mode where the clutch is engaged and the voltage regulator is activated so that the battery can power the motor-generator to provide additional power to the drive train, and (4) a fourth mode of operation where the motor-generator draws power from the drive train to charge the battery thereby providing regenerative braking. In addition to these basic modes, the invention system can also respond to a conditions where the battery is fully charged, no power is needed at the drive train and high pressure steam is being generated. In such a condition, the hot exhaust bypass valve is opened to divert hot exhaust around the boiler and the vapor engine bypass valve is opened to divert high pressure vapor around the vapor engine.